Scsi Raid Controller
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 IBM ASR 2020S ServeRAID 6I U320 Raid Controller SCSI PCIX 71P8627  US $8.95
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 Retail Box LSI LSI21320 R Dual Channel Ultra320 SCSI RAID Controller US $49.00
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Is Your Mission Critical Data Secured By A Raid On Your Server?
Is your mission critical data secured by a RAID array on your server?
RAID is NOT a back up solution!!
RAID is a Redundant Array of Inexpensive Disks, designed by combining multiple disk drives into an array of disks. Why? To yield performance? Yes. To act as backup? No. Yet, many resellers still mistakenly believe a RAID solution sufficiently protects their data, and neglect to backup their mission critical data remotely or to tape. The Mean Time Between Failures (MTBF) of a RAID solution is the MTBF of an individual drive, divided by the number of drives in the array. You're thinking, "Well, wait a second. This means that the MTBF becomes lower, not higher. How does that help?" Keep reading.
Disk arrays are designed to provide fault tolerance by redundantly storing information in a variety of methods.
RAID-0
RAID-0 is a striping solution. In level 0, data is split across the drives, resulting in higher data throughput. Performance is enhanced, but the failure of any disk in the array results in data loss. For improved performance in RAID0 solutions, synchronized spindles are recommended, especially when allocating small stripes. RAID0 solutions provide NO redundancy.
I would only recommend using RAID-O only if the data there is transient, as it WILL be eventually lost. Here especially, maintain remote offsite backups because of the increased risk.
RAID-1
RAID Level 1, on the other hand, does provide redundancy by writing data to two or more drives. Reads tend to be faster, but writes slower as compared to a single drive, however if either drive fails, no data is lost. This is commonly called mirroring and only requires two drives.
If you have a failure of a single drive in a RAID1 array (either software or hardware) all you would have to is put a new drive in and tell the controller (or the software drivers) to rebuild the array. This is considered replacing a failed drive of an existing RAID array.
RAID1 is not economical past four hard drives. RAID1 OS disks are well worth their expense.
RAID-2
RAID Level 2 is intended for use with drives that don't have built-in error detection. Unfortunately SCSI drives do support built-in error detection - not a good mix.
RAID-3
RAID Level 3 stripes data at a byte level across several drives, with parity stored on one of the drives.
RAID-4
RAID Level 4 stripes data (at a block level) across several drives, with parity stored on one drive. Parity facilitates recovery from any failed drive. Read times are the same as RAID0 and writes (even though relatively fast), require parity data to be updated each time.
RAID-5
The difference between 4 and 5 is that parity is spread across all drives in the array. Parity is no longer a bottleneck, but reads are slower than RAID-4. You win some - you lose some.
As the disk count increases in a RAID-5 array, so does the storage efficiency. This is because there is one disk's worth of redundancy (parity) per array. For example a 3-disk RAID-5 has one disk's worth of parity and two disk's worth of usable space, therefore the efficiency is 67%, i.e., 67% of the total disk space is available for user data.
Efficiency = (DiskCount-1) / DiskCount
A degraded RAID-5 is an array with a failed disk. If the user tries to read a block on the failed disk the RAID software will have to access all the other disks in the array to reconstruct that missing data. However if the user tries to read a block on one of the remaining good disks then nothing special happens. The data is simply read from the disk.
RAID -10
RAID10 is a combination of mirroring and striping. Each disk block is completely duplicated on its drives mirror. If a drive in the RAID10 array dies, data is returned from its mirror drive in a single read with only minor performance reduction. What happens though when you lose the mirror drive during recovery? Ouch!
Still most hard drives failures are related to manufacturing defects, so one pro-active approach is to mirror each drive with one from a different manufacturer's lot number. I'm still reading a thread in one forum about massive simultaneous Seagate 1.5TB drive failures. Multiple simultaneous drive failures in any RAID array is not as uncommon as you may think. Think about this. Most companies buy the hard drives they install in servers from preferred vendors, and buy in volume to get discount pricing. If there's a manufacturing defect in that lot of hard drives, the MTBF of each of those drives is very similar. When one drive fails, does it put a heavier load on the remaining drives in the array? Hard drives have moving parts, thus will eventually wear out. RAID cards do fail as well, but that's very rare.
RAID arrays provide a buffer to swap drives without powering down, but it's still very necessary to maintain offsite remote backup in case your server completely crashes. Years ago, I had a client bring in a server that had lightning damage - charred black components - DOA. Minus a RAID array (in this case, the server was fried - LOL), you can still recover from backups. Downtime is the persuasive consideration, as your customers will notice, thus increasing the likelihood of churn. If your site gets hacked or you accidentally delete half your root partition, RAID will provide no protection.
The common (minimum) configurations are 2 drives in RAID-1 and 4 drives in RAID-10 as that is the most economical setup to get an array benefit. RAID-5 can be provisioned with 3 drives to give you a stripe and a parity drive.
Hardware versus Software RAID Solutions
Software RAID solutions occupy their hosts system memory and CPU resources (system dependent) - degrading overall server performance. Hardware RAID solutions allow the host server to execute user applications while the array adapter's processor simultaneously executes the array functions.
What about fault tolerance?
Software based solutions generally require a separate boot drive, which is NOT included in the array. If the boot drive is in the array and it fails, the software array will not boot, as it must be read from the disk and executed from resident memory.
Hardware arrays are highly fault tolerant since its array logic is based in hardware, eliminating the need to boot from software.
Horror stories of multiple simultaneous drive failures in RAID arrays
I've seen threads pop up in forums, a little more frequently, about multiple simultaneous drive failures in RAID arrays. I recall an episode related to Seagate hard drives. Seagate's SD1A firmware update, meant to fix problems with its Barracuda 7200.11 models, only managed to make things worse-bricking the drives of those who bothered to install it. They pulled their update pending validation. Barracuda owners who flashed their disks with the firmware found that after they rebooted, they'd receive a system disk failure error message. Backups, if they were stored on the same drive that was flashed, also became unavailable. Wait a moment! Who does backups on the same drive? I saw one analogy that went like this. It's like installing seat belts in a car, but not allowing you to buckle them until you've been thrown through the windshield.
I've seen threads from quite a few furious OPs in various forums flaming their hosts because their mission critical data was lost forever because of multiple simultaneous drive failures in a RAID array on their server. When they picked their host, they were on the same forums asking for FREE this and FREE that - lowest cost - yet the data they intended to entrust to that host was mission critical to their business. This whole concept slays me. Your data is your business.
My recommendation
My preference is hot swappable hard drives - always have a hot spare, and if possible a second hot spare. Be sure to back up your data remotely and on tape. One hardcore statistic is that over 80% of companies that have lost their data go out of business within one year. Don't allow yourself to be part of that statistic. Don't rely solely on RAID array solutions to protect your data. Make them one part of a disaster recovery and business continuity plan. Redundant solutions (remote and tape back ups) should be a vital component of that plan.
About the Author
Steve Bloemer is the author of the Hostirian News Feed at http://www.hostirian.com.
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HP Storage Controller (Raid) Ultra320 SCSI 320Mbps Raid 1CH AA850A $450 HP Storage Controller (Raid) Ultra320 SCSI 320Mbps Raid 1CH AA850A |
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Intel RAID Ultra320 SCSI Controller PCI-X RAID C76998-002 $54.74 Intel RAID Ultra320 SCSI Controller PCI-X RAID C76998-002 |
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Intel RAID Ultra320 SCSI PCI-X RAID Controller (With Battery) SRCZCRX $40.75 Intel RAID Ultra320 SCSI PCI-X RAID Controller (With Battery) SRCZCRX |
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HP ProLiant Opteron 2.8GHz Serial Attached SCSI RAID Controller 438220B21 $382.38 HP ProLiant Opteron 2.8GHz Serial Attached SCSI RAID Controller 438220B21 |
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Adaptec 2010S Controller Card RAID U320 SCSI PCI 2004000-1-Pack $119.56 Adaptec 2010S Controller Card RAID U320 SCSI PCI 2004000-1-Pack |
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IBM ServeRAID 6M U320 SCSI w/256MB Cache RAID Controller 02R0998 $285 IBM ServeRAID 6M U320 SCSI w/256MB Cache RAID Controller 02R0998 |
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IBM ServeRAID 6M 128MB Ultra320 SCSI RAID Controller 32P0033 02R0985 $83.98 IBM ServeRAID 6M 128MB Ultra320 SCSI RAID Controller 32P0033 02R0985 |
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Intel Storage Controller RAID Serial ATA-300; Serial Attached SCSI SASWT4I $121.25 Intel Storage Controller RAID Serial ATA-300; Serial Attached SCSI SASWT4I |
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Intel RAID Ultra320 SCSI Controller PCI-X RAIDC76998-001 $57.24 Intel RAID Ultra320 SCSI Controller PCI-X RAIDC76998-001 |
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Adaptec 2010S U320 SCSI Controller Card Zero-channel RAID PCI $123.22 Adaptec 2010S U320 SCSI Controller Card Zero-channel RAID PCI |
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Intel Ultra320 SCSI PCI-X RAID Controller SRCU42X $132.75 Intel Ultra320 SCSI PCI-X RAID Controller SRCU42X |
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Intel 8-Ports SCSI RAID Controller Up To 300Mbps 8 X Serial Attached For SR1550 And SR2500 SCSI Falsasmp $40.75 Intel 8-Ports SCSI RAID Controller Up To 300Mbps 8 X Serial Attached For SR1550 And SR2500 SCSI Falsasmp |
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IBM ServeRAID 4Mx Storage Controller (RAID) 2 Channel Ultra160 SCSI 160Mbps RAID 06P5737 $23.47 IBM ServeRAID 4Mx Storage Controller (RAID) 2 Channel Ultra160 SCSI 160Mbps RAID 06P5737 |
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IBM ServeRAID 3L Storage Controller RAID Ultra2 Wide SCSI 80Mbps RAID 0/1/5 PCI 01K7364 $68.85 IBM ServeRAID 3L Storage Controller RAID Ultra2 Wide SCSI 80Mbps RAID 0/1/5 PCI 01K7364 |
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IBM ServeRAID 4Mx Storage Controller With Battery (RAID) 2 Channel Ultra160 SCSI 160Mbps RAID 06P5737 $52.15 IBM ServeRAID 4Mx Storage Controller With Battery (RAID) 2 Channel Ultra160 SCSI 160Mbps RAID 06P5737 |
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Lot of (50) pcs Intel RAID Ultra320 SCSI PCI-X RAID Controller SRCZCRX-50PACK $2023.6 Lot of (50) pcs Intel RAID Ultra320 SCSI PCI-X RAID Controller SRCZCRX-50PACK |
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Intel SRCU32 Ultra-160 SCSI RAID Controller 160Mbps Per Channel 2 X 68pin VHDCI SCSI External 2 X 68pin SCSI Inte... $85 Intel SRCU32 Ultra-160 SCSI RAID Controller 160Mbps Per Channel 2 X 68pin VHDCI SCSI External 2 X 68pin SCSI Inte... |
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Intel 4-Port SAS RAID Controller $91.99 0 1 1E 4 4 x Serial Attached SCSI Internal 4-Port SAS RAID Controller AXX4SASMOD Intel Intel Corporation SAS RAID Controller Serial Attached SCSI www.intel.com |
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SCSI Card 29320ALP-R - storage controller - Ultra320 SCSI - PCI-X $207.99 Adaptec SCSI Card 29320ALP-R - Storage controller - 1 Channel - Ultra320 SCSI low profile - 320 MBps - RAID 0 1 10 - PCI-X |
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ATTO UL5D Dual Channel ULTRA320 SCSI RAID Controller $327.99 0 2 2 x 68-pin VHDCI Ultra320 SCSI - SCSI External 2.71" Height x 6.60" Width 3 Year UL5D Dual Channel ULTRA320 SCSI RAID Controller ATTO ExpressPro-Tools ATTO Configuration Tool Formatting Utility Software The ATTO ExpressPCI UL5D Low-Profile Ultra320 SCSI host adapter is the industry's first low-profile PCIe SCSI host adapter. Utilizing Ultra320 SCSI and next-generation PCI Express (PCIe) technology. With throughput of up to 320 MB/sec. per channel for a combined speed of up to 640 MB/sec., the ATTO ExpressPCI UL5D Low-Profile SCSI host adapter is ideal for integration into enclosures where space is at a premium. Easy to deploy, manage and scale, the UL5D Low-Profile host adapter is the ideal solution for data-intensive environments such as 10-bit high definition video, transactional database applications, email servers and large server farms. ATTO Atto Technology EPCI-UL5D-L00 Mac PC PCI Express x4 Plug-in Card SCSI RAID Controller UL5D Dual Channel ULTRA320 SCSI RAID Controller Ultra320 SCSI Up to 30 Up to 320 MBps Per Channel www.attotech.com |
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HP Smart Array 6402/128 Storage Controller (RAID) 2 Channel Ultra320 SCSI 320Mbps RAID 0 1 5 10 Adg PCI-X $51.71 HP Smart Array 6402/128 Storage Controller (RAID) 2 Channel Ultra320 SCSI 320Mbps RAID 0 1 5 10 Adg PCI-X |
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Intel RAID Controller RS25SB008 - Serial Attached SCSI (SAS) - PCI Express 2.0 x8 - Plug-in Card - RAID Supported - 1, 5, 6,... $1065.77 Intel RAID Controller RS25SB008 - Serial Attached SCSI (SAS) - PCI Express 2.0 x8 - Plug-in Card - RAID Supported - 1, 5, 6,... |
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IBM ServeRAID B5015 SAS RAID Controller - Serial Attached SCSI - PCI Express 2.0 x8 - Plug-in Card 1, 5 RAID Level 46M0969 $694.64 IBM ServeRAID B5015 SAS RAID Controller - Serial Attached SCSI - PCI Express 2.0 x8 - Plug-in Card 1, 5 RAID Level 46M0969 |
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IBM 44E8700 SAS RAID Controller - Serial ATA/300, Serial Attached SCSI - PCI Express x8 - Plug-in Card - 0, 1, 1E RAID Level $192.79 IBM 44E8700 SAS RAID Controller - Serial ATA/300, Serial Attached SCSI - PCI Express x8 - Plug-in Card - 0, 1, 1E RAID Level |
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Cisco LSISAS1064E SAS RAID Controller - Serial Attached SCSI, Serial ATA/300 - PCI Express x8 - Plug-in Card 0, 1, 1E RAID Leve $143.29 Cisco LSISAS1064E SAS RAID Controller - Serial Attached SCSI, Serial ATA/300 - PCI Express x8 - Plug-in Card 0, 1, 1E RAID Leve |
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ATTO Technology / ATTO UL5D Dual Channel ULTRA320 SCSI RAID Controller / EPCI-UL5D-L00 $362.15 ATTO Technology - ATTO UL5D Dual Channel ULTRA320 SCSI RAID Controller - EPCI-UL5D-L00 |
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Compaq Smart Array 5i Storage Controller (Raid) Ultra160 SCSI PCI 228510-001 226593-B21 $144.25 Compaq Smart Array 5i Storage Controller (Raid) Ultra160 SCSI PCI 228510-001 226593-B21 |
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HP Smart Array 641 Storage Controller (RAID) Ultra320 SCSI 1CH PCI-X 291966-B21 $48.25 HP Smart Array 641 Storage Controller (RAID) Ultra320 SCSI 1CH PCI-X 291966-B21 |
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HP Smart Array 641 Storage Controller (RAID) Ultra320 SCSI 1CH PCI-X 291966B21 $61 HP Smart Array 641 Storage Controller (RAID) Ultra320 SCSI 1CH PCI-X 291966B21 |
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HP Modular Smart Array 500 Controller Storage (RAID) Ultra160 SCSI 218252-B21 $81.35 HP Modular Smart Array 500 Controller Storage (RAID) Ultra160 SCSI 218252-B21 |
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Compaq Smart Array 4200 Storage Controller (RAID) Ultra2 Wide SCSI PCI 401859001 $292.11 Compaq Smart Array 4200 Storage Controller (RAID) Ultra2 Wide SCSI PCI 401859001 |
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HP / Compaq Smart Array 4200 Quad Channel ULTRA2 SCSI RAID Controller Card 401859 $293.25 HP / Compaq Smart Array 4200 Quad Channel ULTRA2 SCSI RAID Controller Card 401859 |
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HP Smart Array P410/1GB SAS RAID Controller Serial Attached SCSI Serial ATA/150 PCI E 572532B21 572532-B21 $565.85 HP Smart Array P410/1GB SAS RAID Controller Serial Attached SCSI Serial ATA/150 PCI E 572532B21 572532-B21 |
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HP Smart 3200 Storage Controller (RAID) Ultra2 Wide SCSI PCI 295643-B21 340855-001 $23.95 HP Smart 3200 Storage Controller (RAID) Ultra2 Wide SCSI PCI 295643-B21 340855-001 |
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Compaq Smart 2DH Storage Controller (Raid) Ultra Wide SCSI 40Mbps PCI 295243001 $20.5 Compaq Smart 2DH Storage Controller (Raid) Ultra Wide SCSI 40Mbps PCI 295243001 |
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HP 8-Ports SAS / Serial Attached SCSI RAID Controller 128MB Cache SAS8344ELPHP $234.11 HP 8-Ports SAS / Serial Attached SCSI RAID Controller 128MB Cache SAS8344ELPHP |
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HP Smart Array 641 Storage Controller (RAID) Ultra320 64MB SCSI 1CH PCI-X 291966B21 305414-001 $23.71 HP Smart Array 641 Storage Controller (RAID) Ultra320 64MB SCSI 1CH PCI-X 291966B21 305414-001 |
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Dell Perc 4E/DC Dual Channel PCI Express ULTRA320 SCSI RAID Controller With 128MB Cache and Battery TD977 $380.78 Dell Perc 4E/DC Dual Channel PCI Express ULTRA320 SCSI RAID Controller With 128MB Cache and Battery TD977 |